1. Technical Field
The present invention relates to a technology of displaying a setting state of an area where measurement processing is enabled in a three-dimensional sensor in which a measurement target (hereinafter, occasionally referred to as “workpiece”) and a support surface of the measurement target are imaged with a stereo camera to perform three-dimensional measurement of the measurement target using a produced stereo image.
2. Related Art
The three-dimensional visual sensor includes a function of restoring three-dimensional information on a target by stereo measurement and a function of matching the restored three-dimensional information with previously registered three-dimensional model to recognize a position and an attitude of the target. The three-dimensional visual sensor is used to recognize a component that is a grasping target of a picking robot or to inspect a component or a shape of a completed product.
The applicant developed a general-purpose three-dimensional visual sensor, in which a measurement condition is easily changed depending on the intended use and set contents and processing result can be confirmed on an easy-to-understand screen. For example, Japanese Unexamined Patent Publication Nos. 2006-349586 and 2009-53147 disclose the confirmation display.
In the technique disclosed in Japanese Unexamined Patent Publication No. 2006-349586, after calibration of a stereo camera is performed, a height range to be measured is assigned by a user, a range which is located within the assigned height range and in which a point included in visual fields of all the cameras is projected is determined in each camera, and an image expressing the ranges is displayed. In the display of the technique disclosed in Japanese Unexamined Patent Publication No. 2006-349586, the user can easily confirm whether the stereo cameras are set in a state in which the height range assigned by the user can be measured.
In the technique disclosed in Japanese Unexamined Patent Publication No. 2009-53147, after a z-coordinate of a processing target region is measured with a plurality of cameras including a camera that is set such that the front view of the support surface of the workpiece is imaged, the measured z-coordinate is set to a pixel corresponding to the processing target region in the front view image while zero is set to other pixels as the z-coordinate, and perspective transformation of a three-dimensional pixel distribution generated by the settings is performed to display a produced projection image. In the display of the technique disclosed in Japanese Unexamined Patent Publication No. 2009-53147, even if part of the measurable range is set to the processing target region, the measurement result can be displayed while correlated with an image around the processing target region. Therefore, the user can easily recognize the measurement result.
In the site where the three-dimensional visual sensor is introduced, occasionally an area where the measurement result becomes effective is set from the range where the stereo measurement can be performed. For example, when the three-dimensional visual sensor is used to control the picking robot, the effective area is set such that a location where a robot arm is difficult to be extended or a location where the robot is possibly broken when the robot arm is extended are excluded. When the three-dimensional visual sensor is used for the purpose of inspection, the effective area is set such that a location having no possibility that the inspection target region exists is excluded. When the effective area is set, the recognition result of the region out of the effective area is not outputted.
In order to set the effective area, generally the measurable area is imaged to display the produced image, and a manipulation assigning the range to which the effective area should be set on the display screen. When the range of the effective area is determined on the support surface of the target by the above assignment, three-dimensional information on the effective area is derived based on measurement parameters determined by the calibration, and the three-dimensional information is registered in a memory of the three-dimensional visual sensor.
Occasionally, a range in a height direction of the effective area is determined by accepting the assignment of the measurement range in the height direction.
However, because a size of the image projected to an imaging surface of the camera is decreased as the imaging target is moved farther away from the viewpoint of the camera, it is difficult for the user to recognize how much the set effective area spreads or whether the spread range is proper. The problem is likely to be solved when the effective area can be displayed in the three-dimensional manner along with the measurement target space. However, in order to realize such display, it is necessary to measure pieces of three-dimensional information on all the constituents included in the measurement target space. Therefore, such display is substantially impossible.